Heat pipe with composite wick structure

ABSTRACT

The heat pipe of the invention includes a tube in which an evaporating portion and a condensing portion are defined; a grooved wick longitudinally and entirely disposed on an inner wall of the tube and communicating the evaporating portion with the condensing portion; a porous wick only disposed on the inner wall of the evaporating portion and covering the grooved wick in the evaporating portion; and a fiber wick in a shape of a strip, whose one end connects the porous wick and whose the other end longitudinally extends to the condensing portion.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention generally relates to heat transfer elements, particularly to heat pipes.

2. Related Art

A heat pipe is a heat transfer element which employing phase transition to efficiently transfer heat between two solid interfaces. Usually, an evaporating portion and a condensing portion are separately defined at two ends of a heat pipe. At the evaporating portion, a work fluid within the heat pipe turns into a vapor by absorbing the heat. The vapor condenses back into a liquid at the condensing portion, releasing the latent heat by a heat sink. The liquid then returns to the evaporating portion through either capillary action or gravity action where it evaporates once more and repeats the cycle.

In practice, heat pipes are not always arranged in a direction that the evaporating portion is downward. Sometimes a heat pipe may be arranged reversely or obliquely. This tends to make the work fluid which is in liquid phase and is flowing back contained by gravity. In a traditional heat pipe, the wick structure is placed on an inner wall of the pipe. Thus only a part of wick structure can provide a capillary force to push the work fluid when the heat pipe is slant. The efficiency of flowing back of the work fluid is not good enough.

SUMMARY OF THE INVENTION

An object of the invention is to improve the efficiency of flowing back of work fluid regardless of the direction of heat pipe.

To accomplish the above object, the heat pipe of the invention includes a tube in which an evaporating portion and a condensing portion are defined; a grooved wick longitudinally and entirely disposed on an inner wall of the tube and communicating the evaporating portion with the condensing portion; a porous wick only disposed on the inner wall of the evaporating portion and covering the grooved wick in the evaporating portion; and a fiber wick in a shape of a strip, whose one end connects the porous wick and whose the other end longitudinally extends to the condensing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of the first embodiment of the invention;

FIG. 2 is a cross-sectional view along line 2-2 in FIG. 1;

FIG. 3 is a cross-sectional view along line 3-3 in FIG. 1;

FIG. 4 is a partially sectional view of the first embodiment of the invention;

FIG. 5 shows a typical application of the first embodiment of the invention;

FIG. 6 is a cross-sectional view of the evaporating portion of the second embodiment of the invention; and

FIG. 7 is a cross-sectional view of the condensing portion of the second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Please refer to FIGS. 1 and 4. The heat pipe of the invention includes a tube 10, a grooved wick 11, a porous wick 12 and a fiber wick 13.

An evaporating portion 100 and a condensing portion 101 are defined in the tube 10. In the shown embodiment, the evaporating portion 100 and the condensing portion 101 are separately located at two ends of the tube 10. Of course, there may be a plurality of evaporating portions 100 or condensing portions 101. The grooved wick 11 is longitudinally and entirely disposed on an inner wall of the tube 10 and communicates the evaporating portion 100 and the condensing portion 101. A work fluid (not shown) contained in the tube 10 may flow back from the condensing portion 101 to the evaporating portion 100 through the grooved wick 11.

The porous wick 12 is made of sintered powder. The porous wick 12 is only disposed on the inner wall of the evaporating portion 100 and covers the grooved wick 11 in the evaporating portion 100.

Please refer to FIGS. 2 and 3. The fiber wick 13 is a strip of woven fiber or metallic wires. One end 130 of the strip of fiber wick 13 connects to the porous wick 12 as shown in FIG. 3. For example, the end 130 is sintered together with the porous wick 12 when the porous wick 12 is being sintered. The other end 131 of the fiber wick 13 longitudinally extends to the condensing portion 101 as shown in FIG. 2. In this embodiment, the end 131 of the fiber wick 13 is just placed at the condensing portion 101 without any fastening. Preferably, a cross-sectional area of the fiber wick 13 is about one eighth of that of the tube 10.

As shown in FIG. 5, the evaporating portion 100 is touched by a heat source 2 and the condensing portion 101 is connected with fins 3. When the heat source 2 is generating heat, the work fluid in the porous wick 12 starts evaporating. The evaporated work fluid will move to the condensing portion 101 because the porous wick 12 is only located in the evaporating portion 100. The evaporated work fluid will further condense by releasing heat to the fins 3. Then the condensed work fluid flows back the evaporating portion 100 through the grooved wick 11. If the heat pipe 1 is arranged in a direction disadvantageous to the flowing back of the work fluid, the distal end 131 of the fiber wick 13 will naturally pend because of gravity. The pendent fiber wick 13 will reach and absorb the condensed work fluid to transfer it back to the porous wick 12 in the evaporating portion 100. The efficiency of heat transfer of the heat pipe 1 can be increased.

Additionally, the tube 10 of the heat pipe 1 also can be flat so as to make the fiber wick 13 in the condensing portion 101 gripped by the tube 10 as shown in FIG. 7. But the fiber wick 13 in the evaporating portion 100 is pressed by the porous wick 12 and not touched by the tube 10.

While the forgoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. As such, the appropriate scope of the invention is to be determined according to the claims. 

What is claimed is:
 1. A heat pipe with composite wick structure, comprising: a tube in which an evaporating portion and a condensing portion are defined; a grooved wick substantially longitudinally and entirely disposed on an inner wall of the tube and communicating the evaporating portion with the condensing portion; a porous wick only disposed on the inner wall of the evaporating portion and covering the grooved wick in the evaporating portion; and a fiber wick in a shape of a strip, wherein one end of the fiber wick connects the porous wick and the other end thereof longitudinally extends to the condensing portion.
 2. The heat pipe with composite wick structure of claim 1, wherein the evaporating portion is located at one end of the tube.
 3. The heat pipe with composite wick structure of claim 2, wherein the condensing portion is located at the other end of the tube.
 4. The heat pipe with composite wick structure of claim 1, wherein the porous wick is sintered powder.
 5. The heat pipe with composite wick structure of claim 4, wherein one end of the fiber wick is sintered together with the porous wick.
 6. The heat pipe with composite wick structure of claim 1, wherein one end of the fiber wick is sintered together with the porous wick.
 7. The heat pipe with composite wick structure of claim 1, wherein the fiber wick is woven fiber.
 8. The heat pipe with composite wick structure of claim 1, wherein the fiber wick is woven metallic wires.
 9. The heat pipe with composite wick structure of claim 1, wherein the other end of the fiber wick is placed in the condensing portion without fastening.
 10. The heat pipe with composite wick structure of claim 1, wherein the tube is flat in shape and the fiber wick in the condensing portion is gripped by the tube. 